Unsound usages of unsafe implementation about c_void

[llooFlashooll]

Hi, I am scanning this crate in the latest version using my own static analyzer tool.

Unsafe pointer conversion is found at:

let read_size = glfs_pread(
    self.file_handle,
    fill_buffer.as_mut_ptr() as *mut c_void,
    count,
    offset,
    flags,
);

This unsound implementation would create memory issues such as overflow, underflow, or misalignment. The attacker can manipulate the argument count, offset associated with the c_void pointer with a large value, which can lead to a buffer overflow bug. The c_void pointer and its associated size argument are passed through the FFI (glfs_pread), which can further corrupt the C/C++ code.

This would cause undefined behaviors in Rust. Adversaries can manipulate the associated size argument to cause memory safety bugs. I am reporting this issue for your attention.

[cholcombe973]

Thanks for finding this. Would you like to put up a fix as well? If not I'll try to get to it when I can.

[llooFlashooll]

Thanks for your timely reply! I will further provide a PoC as well as a fix later.